As it is known, the technical word "rod" serves to indicate a structural part, subject to traction or pulling efforts.
The connotation given to this word in the present patent is applied to steel bars, cables and wires, which are introduced into the soil and serve to transfer the applied efforts at one free end or "head", to a sector in the other end, called an anchorage sector, and where the traction forces are transferred through, is called a "free sector".
Thus, the applied efforts on the rod head pass through the free sector and are transferred by means of the anchored sector or anchorage bulb.
The rod head consists of a device for fastening the armature--bars, cables, wires or steel tubes--to the supporting framework.
The anchorage bulb is made up through injection, usually of cement prime, but may be also of resin. When this injection is made by gravitation, this type of rod is called an anchor bolt. The anchor bolts are not further discussed in this application, since the rods described herein are those which have its bulb formed by injection, under pressure.
The rods differ one from another, basically by the
perforation process PA1 type and armature arrangement PA1 device and injection process PA1 head anchorage device PA1 slope stabilization PA1 staying of walls subject to thrusts PA1 fastening of frameworks subject to a secondary force PA1 fastening of vaults or tunnel walls PA1 fastening of concrete dams PA1 fastening of transmission towers from a electrical network and others. PA1 1st group--BAUER system PA1 2nd group--SOLETANCHE
The differences relative to the perforation process are not essential for the purpose of this application, since the invention disclosed herein refers to the armature arrangement, in the injection devices and process, and to the complete rod protection.
The rods anchored in the soil or rock or, the anchorages, as they are usually called, have several usages in engineering, such as:
The making of rods faces, up to the present technical level, the challenge of its basic desideratum: that is, to introduce an armature into the soil which, by its very nature, must be protected against the environment agressivity, and later on, subject this armature to a certain pulling out effort.
The problem consists in trying to avoid, not only the direct contact of the rod armature with the agressive environment, in order to preserve it against corrosion, but also to provide a complete steel protection, in the long run.
This problem is even more difficult to solve, when one knows that such protection cannot avoid the formation of a great amount of friction soil/cement, that serves as a basis for the anchorage.
For this purpose, the prior art processes and apparatuses may be grouped, as follows:
TUBFIX system (injected tubular anchorages) - SUISSBORING
In the 1st group, are the main systems, which are characterized by the inclined point of the perforation rod.
TUBFIX--The TUBFIX anchorage, from Suissboring Co., consists in introducing into the soil, an adequate tube by rotation, so that the crown is lost in the soil and constitute, together with tube, the rod armature.
The lower part of the tube--or anchorage sector--is perforated and "inlaid", allowing the injection liquid to flow out, to form the bulb.
The protection of the tubular armature is made by means of galvanization.
BAUER--The BAUER procedure, of German origin, consists in introducing a tube, having inside a steel bar of high strength, through a lost point, which guides the tube.
The bulb injection is done at the same time as the tube is extracted, the injection flowing out by the end and through the ringed gap between the tube and the steel shaft.
The free sector is protected by means of a plastic sheath.
To the 2nd group belongs the anchorages made up of wires (or even cordages) placed around a central tube, whose main representative is the rod type SOLETANCHE.
SOLETANCHE--In this system, the ringed gap among the wires is occupied by an internal tube lost and blind in the free sector and provided with holes in the anchorage sector, where from the injection liquid flows out, to form the bulb. These holes are closed by "inlaids"--which surround the sheaf which prevent the liquid flowing back inside the tube.
A secondary operation closes the tube above and under each inlaid, injecting the liquid under pressure, which "bursts" the inlaid, and fills the gap between the rod and the soil.
The free sector remains protected by a plastic sheath.
Certain disadvantages peculiar to each of the above systems are stated as follows:
TUBFIX--The tubes junctions, whether by sleeve or welding, is a critical point, that cannot remain ignored and must receive special care, like traction tests, welding survey, etc.
On the other hand, the tube protection by galvanization increases the cost of the rod, rendering it very expensive.
BAUER--The possibility of introducing an anchorage type BAUER is restricted to soils without cohesion (sandy soils, rough soils, without blocks or obstacles).
In all other cases of cohesive soils (as clay, argilite or sandy soils) the use of BAUER type rods, is subject to the following procedure:
Making of a rotative perforation, with a diameter greater than necessary, for the rod installation:
Filling of hole with sand (gross).
This procedure have (among other) the disadvantage of making expensive the cost of rods.
SOLETANCHE--The anchorage sector cannot protect entirely the rod steel.
Usually, the introduction of the rod in holes, where there is no danger of collapsing of the walls, makes the coating unnecessary. In this case, we can't avoid the armature touching the ground, mainly in the case of tilted or horizontal rods: when placed, the rod touchs the ground with its point and/or with its spacers and the material so removed, stays among the wires.
This could be avoided, if we use systematically the covering tube for introducing the rod, taking it out some time after the injection; as a matter of fact, this procedure is usual only in holes subject to falling down.
Even with this careful procedure, there remains the danger of the direct contact steel and ground, for, when removing the covering, the injection overflowing, not yet hardened, will have the tendency of flowing to the space occupied by the tube wall, leaving the flowing column, which is supported by the spacers.
Some technics use the system of increasing the covering thickness of the armature, by means of spacers, taking the risk of two main inconvenients:
(a) the greater the spacer, the greater the base for the flowing column, and greater the column weight right down, and so, greater the tendency to separation;
(b) the increase in the perforation cost, due to the increase of spacers diameter.
in Brazilian Pat. No. 7019728, the applicant aimed the protection of the new process and device for making rods anchored in soils or rocks, and even, if for eventual reinjections, the operation should end by the washing of the inside chambers of the device, by water flowing, the above mentioned inconveniences, have been overcome with the improvements.
Further, a grooved tube of permanent material, placed in the anchorage sector, in order to provide the weight transfer from the rod armature to the soil, and provide also and additional protection of the steel against corrosion, due to the passage of cemente mud, according to the present standards.
The technique, now improved, is based upon the erection of an anchorage, through injection and repeated injections, all under pressure, of cement mud or chemical products, in the soil or rock.